Process and apparatus for the continuous casting of steel



July 29, 1969 HIROSHI YOSHIDA ETAL 3,457,984

PROCESS AND APPARATUS FOR THE CONTINUOUS CASTING OF STEEL Filed Sept. 7,1966 '7 Sheets-Sheet l 25 24 3 r g "m July 29, 1969 HIROSHI YOSHIDA ETAL3,

PROCESS AND APPARATUS FOR THE CONTINUOUS CASTING OF STEEL Filed Sept.'7, 1966 7 Sheets-Sheet 2 July 29, 1969 HIRDSHI YOSHIDA ETAL 3,457,934

PROCESS AND APPARATUS FOR THE CONTINUOUS CASTING OF STEEL Filed Sept. 7,1966 7 Sheets-Sheet 3 July 29, 1969 HIROSHI YOSHIDA ETAL 3,

PROCESS AND APPARATUS FOR THE CONTINUOUS CASTING OF STEEL Filed Sept- 7,1966 '7 Sheets-Sheet 4 July 29, 1969 HIROSHI YOSHIDA ETAL 3,457,984

PROCESS AND APPARATUS FOR THE CONTINUOUS CASTING OF STEEL Filed Sept. 7,1966 7 Sheets-Sheet 5 y 29, 1969; HIROSH! YQSHIDAI ETAL 3,457,984

PROCESS AND APPARATUS FOR THE CONTINUOUS CASTING OF STEEL Q Filed Sept.7, 1966 7 Sheets-Sheet 6 Fig .20.

July 29, 1969' HIROSHI YOSHIDA ETAL 3,457,934

PROCESS AND APPARATUS FOR THE coNTINUoUs CASTING OF STEEL Filed Sept. 7,1966 7 Sheets-Sheet 7 F lg .30,

g 6 3 -\.LQ D. I O: 5 6 E 3133 a. g Q Thckness of a 4 steel striphn ySOCLength of longest side of ca se' L) United States Patent Oflice3,457,984 Patented July 29, 1969 3,457,984 PROCESS AND APPARATUS FOR THECONTINUOUS CASTING OF STEET. Hiroshi Yoshida, Hideo Okabe, Kenji Sasakr,II IIOShI Nonaka, and Kichizaemon Nakagawa, Chiba-sh], and KiyoyukiIgarashi, Narashino-shi, Japan, assignors to Kawasaki Steel Corporation,Kobe-sh], Hyogo-ken, Ja an a cor oration of Japan p Filed Sept. 7, 1966,Ser. No. 577,695 Claims priority, application Japan, Oct. 1, 1965, 40/60,061 Int. Cl. 322d 11/00 US. Cl. 164-86 Claims ABSTRACT OF THEDISCLOSURE In a method and apparatus for continuous casting comprising:the combination of conveying a plurality of steel strips of indefinitelength over deflector rolls in a downward vertical direction, thedeflector rolls cooperating with auxiliary forming rolls producingprotruding flanges on the edges of said strips, conveying additionalsteel strips of indefinite length over additional deflector rolls in adownward vertical direction adjacent to the first-mentioned steelstrips, said additional deflector rolls cooperating with additionalauxiliary forming rolls to form flanges on the edges of the additionalsteel strips and to further shape the flanges of the first-mentionedsteel strips and introduce the flanges of the adjacent steel strips inlapped relationship, and further including joining means to form sealsof the lapped flanges to produce an open-ended polygonal tubular hollowbody adapted to receive continuous casting of molten metal, the presentinvention further being provided with means for cooling the tubular bodyand a guide assembly, insertable in the open end thereof and acting as asplash guard and cooperating with the forming rolls to insure passage ofthe steel strips over the deflector rolls.

This invention relates to a process and apparatus for the continuouscasting of steel, and more particularly to a process and apparatus forthe continuous casting of an indefinite length of steel strand frommolten steel.

Many processes have been developed to improve the art in the continuouscasting of steel, and one of the most practical processes nowcommercially available is the so called reciprocating mold type processusing a reciprocating motion of an open-ended mold from the bottom ofwhich steel strand is withdrawn. However, the reciprocating mold processinvolves considerable expense in construction as well as maintenance dueto the complicated mechanism of reciprocating motion. In addition, thereis a danger that a solidifying skin formed on the castisg may be brokenby the friction or impact of the mold as it reciprocates causing moltensteel to flow from the damaged casting. Therefore, to prevent thispossibilty of casting damage, the cross sectional area of the steelstrand is reduced and the withdrawal speed of the strand is slowedthereby reducing productivity.

There has also been proposed a continuous casting process using anendless chain conveyor mold constituted by an inclined mold chamberthrough which a continuous strand of steel is withdrawn in a downwardlyinclined direction, In this process the problem of sealing of the moldelement joints has not been successfully overcome thereby causingdifliculty in cooling the mold elements as well as limiting the strandwithdrawal speed and pro dueing many surface defects on the strand.

Other processes which have been proposed but never widely used are thecontinuous casting of metal using metal strips or bands which movedownwardly to form a continuous casing. The molten metal is poured intothe casing formed by the strips or bands where it solidifies with thestrips or bands. Further, a process has been proposed wherein a tubularcasing is formed by a strip and molten metals such as copper and brassare poured in the casing. However, many difiiculties have occurred withthe use of these processes in steel casting because of a low heatconductivity, a high melting point and a high specific gravity of steel.The primary problem is the complete enclosing of the molten metal. Thisis of extreme importasce since the outside strips or bands are liquidcooled and damage to the casting will occur if any of the cooling fluidshould penetrate into the solidifying casting. Also, if the enclosingstrips or hands are not sealed tight, leakage of the molten steel may beappeared. An additional problem is that the joints of the metal stripsor bands must be of suflicient strength to prevent possible separationdue to the static pressure of the poured molten steel. Yet anotherproblem is that bulging of the steel strips or bands will occur unlessthey are of sufficient thickness. This will limit the casting speed andthereby reduce productivity.

Therefore, it is a primary object of the present invention to provide aprocess and apparatus for the continuous casting of steel which willovercome all of the above as well as other problems and deficiencies ofpreviously used casting methods.

Another object of the present invention is to provide a process formaking an indefinite length of steel strand from molten steel with ahigh productivity rate.

A further object of the present invention is to provide an apparatus forthe production of steel strand having a good surface quality in aninexpensive and highly eflicient manner.

Another object of the present invention is to providet an apparatus forforming a continuous casing which will be clompletely sealed to preventany leakage of the molten stee Still another object of the presentinvention is to provide a process and apparatus for making a metal cladobject having a core made of a metal such as steel.

A further object of the present invention is to provide an apparatuswhich is of relatively simple construction and easy to manufacture,which is automatic and rapid in its operation, and which is Well adaptedfor the purposes described.

According to the present invention, the foregoing and other objects areattained by providing a continuous casting process and apparatus whereinmolten steel is directly poured into a polygonal tubular hollow casing(hereinafter referred to as continuous case) of a desired section whichis formed by a plurality of steel strips or bands. This continuous caseoperates to define the cross section of the steel strand to becontinuously cast and to trans mit outwardly the sensible heat of themolten steel. In this regard, the continuous case functions like a moldbut travels together with the steel strand, and, therefore, the caseitself becomes an outer skin of the strand.

The specific nature of the invention as well as other objects, uses andadvantages thereof will clearly appear from the following descriptionand from the accompanying drawings, in which:

FIG. 1 is a side elevation view, partly in section, of the apparatus ofthe present invention;

FIG. 2 is a front elevational view, partly in section, of the apparatusof the present invention;

FIG. 3 is a perspective view of the continuous casting apparatus of thepresent invention;

FIG. 4 is a horizontal sectional view of the first forming stage;

FIG. 5 is an enlarged view of a portion of FIG. 4 clearly depicting thefirst forming operation;

FIG. 6 is a horizontal sectional view of the strips forming thecontinuous case at the first forming operations without showing theforming apparatus;

FIG. '7 is a horizontal sectional view of the second forming stage;

FIG. 8 is an enlarged view of a portion of FIG. 7 clearly depicting thesecond forming operation;

FIG. 9 is a horizontal sectional view of the strips forming thecontinuous case at the second forming operation without showing theforming apparatus;

FIG. 10 is a perspective view of a guide assembly used in the apparatusof the present invention;

FIG. 11 is a vertical sectional view taken along the line xx of FIG. 10;

FIG. 12 is a vertical sectional view taken along the line yy of FIG. 10;

FIG. 13 is a horizontal sectional view of the seam welding operation;

FIG. 14 is a horizontal sectional view of the strips forming thecontinuous case after the welding operation;

FIG. 15 is a sectional view similar to FIG. 11 showing a modified guideassembly;

FIG. 16 is a sectional view similar to FIG. 12 showing another view ofthe modified guide assembly;

FIG. 17 is a horizontal sectional view showing a modification of theforming rolls consist of single stage;

FIG. 18 is an enlarged view of a portion of FIG. 17 clearly depictingthe forming operation using the forming rolls of FIG. 17;

FIG. 19 is a horizontal sectional view of the strips forming thecontinuous case at the forming operation using the forming rolls of FIG.17;

FIGS. 20-22 are horizontal sectional views showing various forms ofmultiple lapping of the edges of the strips forming the continuous case;

FIG. 23 shows the successive forming steps of the multiple lapping ofFIG. 20;

FIGS. 24-29 show various forms of mechanically joining the edges of thestrips forming the continuous case; and;

FIG. 30 is a graphic chart showing the relationship between theproduction rate and the length of the longest side of the case in crosssection and the thickness of the strip forming the continuous case.

Referring now to the drawings, as shown in FIGS. 1-3, the molten steelis continuously poured from a ladle 1 through a tundish 2 into arectangular continuous case 5 formed by steel strips 3, 3, 4 and 4.Although this preferred embodiment uses four strips to form arectangular continuous case, it will be appreciated that more or fewerstrips will be required depending on the cross section desired for thecontinuous case.

The continuous case 5 filled with molten steel therein is supported atthe outside thereof by a plurality of roller supports 6 and 7 whilebeing cooled by high pressure water discharged from a plurality of spraynozzles (not shown) provided on the conduit pipes 8, 9 of the coolingmeans. The molten steel 10 in the continuous case 5 is cooled by thecooling means due to its surface contact with the inside surfaces of thecontinuous case 5. As shown in FIGS. 1

and 2, the molten steel 10 is solidified from the outer surfaces incontact with the continuous case 5 inwardly to the core thereof to formthe steel strand 11.

The steel strand is withdrawn by a suitable mechanism (not shown) insynchronism with the downward movement of the continuous case 5. Themechanism to withdraw the steel strand may also be used for moving thecontinuous case 5 downward or two separate mechanisms can be provided.As the steel strand and the continuous case 5 are being withdrawn,either the case 5 can be pulled off the steel strand by suitable meansor the steel strand and case 5 can be left joined.

A fundamental idea of the present invention will be obtained from theabove description. In carrying out the present invention, it isunderstood that the following conditions and requirements will be met.

First, it is required that each joint of adjacent strips which form thecontinuous case be tightly sealed to prevent the molten steel fromflowing out therefrom or the cooling water from penetrating thereinto.If the tightness of the joint seals is defective permitting coolingwater to penetrate into the continuous case, the quality of the steelstrand would not only be lessened but it would give use to the danger ofan explosion. Further, as is obvious, the flowing out of the moltensteel would produce a condition requiring stoppage of production.

Second, each joint of adjacent strips should be of suflicient strengthso that the joints will not fail and separate due to the ferrostaticpressure of the poured molten steel.

Third it is necessary that the sheet thickness of the steel strips usedfor constructing the continuous case should be sufficiently thick toprevent the case from bulging outwardly. Any slight bulging would makeit impossible to maintain the desired cross sectional shape of the steelstrand and further, it would lead to the breakage of continuous case.

Tests have shown that the sheet thickness will be limited by thecontinuous casting speed (withdrawal speed) and other operatingconditions such as section dimension. The relationship between thewithdrawal speed and the sheet thickness is shown in the followingempirical formulas:

where From the formula, it is seen that the larger the section of steelstrand and the thinner the sheet thickness of the steel strip, thesmaller the possible maximum speed of withdrawal. FIG. 30 is a graphicchart showing the allowable maximum value of the withdrawal speed (V) ofsteel strand at various lengths (L) of the longest side of continuouscase in cross section for different steel strip thicknesses (m).

On pouring the molten steel, it has been found that there will ariseturbulence of the molten steel due to the pouring stream thereof and asolidifying thin shell will be washed off. Sometimes, this washing 01fmay attack the continuous case. In this event, the greater the stripthickness, the less the danger of breakage.

Therefore, it follows that the thicker the steel strip, the safer itsoperation. However, with the increase of sheet thickness, theconsumption of steel strip will be increased with the result that itwould be not only economically disadvantageous, but also the forming andjoining of the continuous case would be difficult. It has been foundthat the thickness of the steel strip should be in the range of 0.2 to3.2 mm. and preferably 0.6 to 1.6 mm.

The outside of the continuous case is sprayed with a cooling fluid suchas water supplied by the cooling means. It will be apparent that thevolume of cooling water employed .depends upon the thickness of thesteel strip, the cross section, and the withdrawal speed of the steelstrand. Tests have shown that approximately 0.2 ton of water per squaremeter of the surface area of the continuous case every minute isrequired for proper cooling. This volume of water is required becausethe temperature of the surface of the continuous case should not behigher than the temperature of 600 C. when the molten steel having thetemperature of 1500-1600" C, is poured into the continuous case, andfurther, the undesirable expansion of the continuous case must belimited.

Discussing now more specifically the preferred embodiment of theinvention illustrated in FIGS. 1-14, two steel strips 3, 3 of relativelywide sheet and two steel strips 4, 4 of relatively narrow sheet areutilized to form a continuous case 5 having a rectangular cross section.In this embodiment, the apparatus used in connection with the strips 3,3 or 4, 4 is symmetrical, and the Working process in connection with thestrip joints is also symmetrical, and therefore, only one strip or onestrip joint will be discussed to simplify the description.

The wide strip 3 is continuously supplied from a reel 13 where it passesthrough a pair of pinch rollers 14 and a plurality of side guides 15into a space between a deflector roll 16 and an upper curved portion 18of a guide assembly 17 whereby the strip 3 is deflected by the deflectorroll 16 in a vertical downward direction.

As shown in FIGS. 10 to 12, the guide assembly 17 comprises twoduplicate sections each having a pair of upper curved portions 18, apair of wide vertical portions 24, a lower curved portion 31, a narrowvertical portion 39 and a protector wall 100. The guide assembly 17 ispreferably formed in two sections to -simplify construction and topermit relative adjustment between the sections to aid in accommodatingthe steel strips 4. The guide assembly protects the forming means fromany splashing of the molten steel as it is being poured into thecontinuous case 5. The guide assembly also prevents any splashing of themolten steel on to the inner surfaces of the continuous case 5 whichwould tend to roughen the inner surfaces of the continuous case 5.

In addition to deflecting the wide strip 3 vertically downward thedeflector roll 16 also is part of the first forming stage 22 shown inmore detail in FIGS. 4 and 5. The deflector roll 16 comprises acylindrical middle portion 19' and two frusto-conical portions 19, 19.Cooperating with the deflector roll 16 are a pair of forming rolls 21with frusto-conical portions 20. The frusto-conical portions 19, 19 onroll 16 complement frusto-conical portions 20 on rolls 21 to bend thesteel strip 3 between them.

The two wide deflector rolls 16 and the four complementary forming rolls21 along with upper curved portions 18 of the guide assembly 17 comprisethe first forming stage 22.

As the steel strip 3 passes through the first forming stage 22, bothedges of strip 3 are bent at an angle of about 45 to form flanges 23, 23as shown best in FIG. 6. To make this forming angle as large as possiblewould be advantageous for the subsequent forming steps, however, theinitial forming bend is limited by the mechanical properties of thesteel strip, the sheet thickness and the diameter of the forming rolls.It has been found where preforming with deflecting is carried out, abending angle up to approximately 75 can be easily achieved with theflange width preferably in the 10 to 20 mm. range. In this forming step,the strip 3 passes through a gap between the wide deflector roll 16 andthe wide vertical portion of the guide assembly 17 to attain an accurateforming of the strip 3.

From the first forming stage 22, the pre-forrned strip 3 with theflanges 23, 23 at both edges is passed into the second forming stage 27comprising narrow deflector rolls 25, and wide forming rolls 26, 2 6.

Narrow steel strip 4 is continuously supplied from a reel 28 betweenpinch rolls 29 and side guides 30 into a space between narrow deflectorroll 25 and the lower curved portion 31 of the guide assembly 17 wherethe strip 4 is deflected to a vertical downward direction into secondforming stage 27 to meet preformed strip 3.

In the second forming stage 27, the narrow deflector rolls 25 comprise acylindrical body the axial length of which is equal to the Width ofnarrow strip 4. The wide forming roll 26 comprises a cylindrical body 33and a cylindrical body 34 of reduced diameter at each end of saidcylindrical body 33.

The edge of narrow strip 4 together with the partly bent flange 23 ofwide strip 3 is introduced in lapped relation into the gap between theroll surface end of the narrow deflector roll 25 and the annular end 37of the wide forming roll 26. As a result, the flange is bent to an angleof approximately whereby the flange 23 and the end of strip 4 are lappedto form a protruded lapped portion or lapping 38. All during thisoperation, the strips 3 and 4 are accurately aligned by the verticalportio 4 and 39, respectively, of the guide assembly 17.

The four strips 3, 3 and 4, 4 form a rectangular body with fourprotruded lappings 38, the cross sections of which is clearly shown inFIG. 9. To form sealed joints at lapping 38, the lapping 38 must becompletely sealed together to prevent penetration of the cooling Wateror outflow of the molten steel.

In FIGS. 1 to 3 and 13, there is shown the preferred embodiment of usingseam welding to seal the lappings 38. The welding means 40 comprises aseam welder 41 at each corner.

Each seam welder 41 has a pair of rotary electrodes 42 and 43 and an aircylinder 44 which urges one electrode 42 toward the other electrode 43.A pair of holding rolls 45 are provided immediately above the rotaryelectrodes to hold the lappings 38 tightly. The four lappings 38 arepressed and electrically welded in a vertical direction as they passbetween rotary electrodes 42 and 43. The rotary electrodes 42 and 43 mayor may not be driven. Thus, the completely sealed continuous case 5 ofprescribed cross section as shown best in FIG. 14 is formed from foursteel strips 3, 3 and 4, 4.

It will be understood that the above description is of a preferredembodiment for manufacturing the continuous case 5. However, theinvention is not limited to this embodiment and may be carried out bythe use of certain modifications which are described below.

The cross section of the continuous case 5 may be of any suitablepolygonal shape besides the preferred rectangular shape. The number ofsides of the polygonal cross section to be formed will determine thenumber of steel strips required.

In order to obtain the perfectly sealed continuous case, it is necessaryto use a steel strip free from any variations in sheet width and whichwill be correctly aligned on the deflecting and forming rolls. To thisend, the edges of the strip should be trimmed in advance of formingpreferably by providing a side trimmer (not shown) in the processingline as the strip leaves the reel. In addition, the use of side guidesor other types of edge position controllers are essential for properalignment of the strip.

In the above-described embodiment, the deflector roll 16 performed adeflecting function as well as a forming function. This dual functionwas used in order to make the distance between the molten steel level inthe case and the tundish nozzle as short as possible. It will beapparent to one skilled in the art that the deflector roll may beseparate from the forming roll. If made separate, the deflector rollneed not be a rotatable roll but may be a fixed curved member. Theroller supports 6, 7 may also be fixed curved surfaces and in manyinstances the support 7 may be omitted for the narrow width steel strip4.

In the guide assembly 17 described in the preferred embodiment, eachsection included the wide vertical portion 24 and the narrow verticalportion 39 formed integral with each other. It will be appreciated thatthese portions 24 and 39 can be separately formed since each portiondeals with a difierent steel strip.

It has been found that the proximity of the guide assembly 17 to themolten steel can sometimes produce heating problems which can affect theguiding elements of the assembly. To prevent this overheating problem,there is shown in FIGS. 15, 16 a guide assembly 47 which is similar inall respects to guide assembly 17 having upper curved portions 18', widevertical portions 24' and narrow vertical portions 39 with the additionof a water jacket 46 having piping 46 to circulate the cooling water.

There is shown in FIGS. 17, 18 a forming assembly 48 which willsimultaneously perform the deflecting and forming operations to producea continuous case having a modified form of lapping. In thismodification, the edges of strips 3 and 4 are bent at an angle of 45 toform flanges 49 and 50 whereby the lapping 51 as best shown in FIG. 19is produced. The forming assembly 48 consists of wide strip rolls 54having frusto-conical portions 52 at its ends and narrow strip rolls 55having frustoconical portions 53 at both ends. This forming assembly 48can attain an operation of deflection and formation in a single step. Inthe single step flange forming, a bending angle in the range of to 75 ispreferred.

In place of the above mentioned single lappings, double lappings 59, 60and 61 shown in FIGS. to 22 are easily formed. For example, in referenceto the double lapping 59, a series of forming assemblies, illustrated inFIG. 23, af may be utilized.

Various designs of forming assemblies can be used depending on theproperties and thickness of the steel strips, the cross section of thecontinuous case, and the type of lapping desired.

In the preferred embodiment discussed above, the seam welding byelectric resistance is shown, although any welding process, such asfusion welding, pressure welding and brazing may be employed. However,the seam welding method is the most suitable method for the high speedcontinuous welding required. to firmly seal the lappings together, othervarious mechanical joining methods may be used in addition to thewelding procedure already discussed. Several examples are shown in FIGS.24 to 29. FIG. 24 shows the formation of a joint 63 by bending thedouble lapping 59 at an angle of 90. FIG. shows a mechanical jointformed by placing a groove in the double laping 59 with a set ofgrooving rolls 64 and 65.

Another joining method shown in FIG. 26 can be applied to both singleand double lappings. In addition to the steel strip for use in thecontinuous case, a narrow steel strip 67 having notches 68 is formedinto a V-shape by a series of rollers 69, 70 and a guide member 71whereby it surrounds a lapping joint 72. A series of rollers 73 and 74apply pressure to steel strip 67 to obtain a firm reinforced joint 75.

The mechanical joining methods shown in FIGS. 27 to 29 can also beapplied to either single or double lapping. The process of FIG. 27utilizes a cut out tongue piece 76 from the lapping 77 which is foldedalong the lapping 77. In FIG. 28, there is shown the use of rivets 78 toform a tightly sealed lapping 79 and in FIG. 29, fasteners 80 are usedto join the lapping 81.

EXAMPLE The continuous case was made by the two stage forming means withseam welding as described in detail in the embodiment of FIGS. 1l4. Alow carbon cold rolled steel strip having a thickness of 0.6 to 1.0 mm.was employed as the strip material for the continuous case. The mainforming roll of the forming means was 150 mm. in diameter. The width ofeach lapping at the four corners of the continuous case was 15 mm. Thelapping was con tinuously welded by a pair of rotary electrodes having adiameter of 200 mm. The continuous case was cooled by water applied atthe rate of about 0.4 ton per square meter of surface area every minutesat a pressure of 4.5 kilograms per square centimeter. The molten steelwas an ordinary carbon steel with a chemical analysis of: (MS-0.17%carbon, 0.220.36% silicon, 0.63-1.22% manganese, 0.0l0-0.0l8%phosphorus, 0.01 l0.024% sulfur, and the balance iron. The temperatureof the molten steel was about 1500 C.

The following table shows the withdrawal speed of the steel strand andthe casting productivity under the above conditions when the thicknessof the steel strip and the continuous case cross section are varied.

TABLE Continuous Withdrawal I case section Thickness of speed, n1./Productiv- Example size, mm. strip, mm. min. ity, t./hr.

250x900 1. 0 2. 2 223 250X900 0. 6 1. 4 144 250x1, 500 1.0 1.0 250X1,500 0. 6 0. 7 118 It has been proved that a high casting productivityand an excellent advantage are obtained by the present invention. Inaddition, it has been found that the steel strand thus produced inaccordance with the present invention has a surface quality at least asgood as the product produced by conventional casting processes.

In the foregoing example, a continuous casting product from an ordinarycarbon steel was described; however, it will be appreciated that allgrades of steel used in continuous casting processes can readily be usedin the present invention.

Thus, there has been provided an eflicient and economical continuouscasting process and apparatus which are well adapted to attain the endsand objects set forth in the description, and which may be readilymodified in several ways so as to best adapt the process or apparatus tothe conditions of the particular casting operation.

It will be understood that variations of the process as outlined aboveand of the apparatus for carrying out the process may be made within thespirit and scope of the invention hereinbefore set forth and hereinafterclaimed.

What is claimed is:

1. A process for the continuous casting of steel comprising:

supplying a plurality of steel strips to a position adjacent a supplyvessel containing molten steel, moving said strips in a verticaldownward direction to make an open-ended tubular hollow body, formingthe edges of said strips into protruded lappings at each corner of saidbody,

joining said lappings of said body to make a sealed continuous case,

pouring said moten steel into said case,

cooling and supporting said case to solidify said molten steel and toprevent bulging of said case, and withdrawing said cast steel downwardlyat a speed of a value of V given by the following formula:

2. Apparatus for the continuous casting of steel comprising:

a plurality of steel strips of indefinite length,

a deflecting roller associated with each steel strip for moving saidsteel strip in a vertical downward direction to make an open-endedpolygonal tubular hollow body, at least some of said deflector rollsbeing provided with frusto-conical end portions,

an auxiliary forming roll of frusto-conical configuration cooperatingwith a frusto-conical end portion of said deflecting rolls to provideflanged edge portions on at least some of said steel strips,

means for introducing the flanged edges of some of said strips in lappedrelationship with the edge portions of the remaining steel strips, saidmeans being adapted for bending said flanged portions in complementaryconfiguration with the edge portions of said remaining steel strips,

means for joining said lapped edge portions to make a sealed continuouscase,

means for supplying molten steel into said case, a plurality ofvertically spaced roller supports abutting and extending the width of arespective steel strip of said case,

a conduit pipe provided with a plurality of spray nozzles located belowand adjacent each of said roller supports and extending axially thelength thereof for discharging a coolant over the surface of said joinedsteel strips, and

means for withdrawing said cast steel downwardly.

3. The structure as recited in claim 2, wherein said auxiliary formingrolls comprise deflecting rolls for said remaining said steel strips,each of said forming rolls being provided with frusto-conical edgeportions cooperating with the edge portions of adjacent deflector rollsto form lapped, adjacent flanged edge portions on adjacent steel strips.

4. The structure as recited in claim 2, wherein said joining meansincludes Welding apparatus provided with rotary electrodes engagingopposed surfaces of the lapped edge portions.

5. The structure as recited in claim 2, and further including:

a forming guide assembly including means cooperating with saiddeflecting rollers for insuring passage of the steel strips over thedeflecting rollers and additional means insertable in the polygonalenclosure for providing a guard for the splashing of molten metalintroduced into the polygonal enclosure.

References Cited UNITED STATES PATENTS J. SPENCER OVERHOLSER, PrimaryExaminer R. SPENCER ANNEAR, Assistant Examiner US. Cl. X.R.

